Measurement of itch.

Measurement in its broadest sense can be defined as the assignment of numerals to objects or events according to rules. The rules settle the scale level, which in turn determines the mathematical and statistical operations permissible when handling the data. Itch is a subjective symptom that can be assessed only by the subject himself. No animal models are established for the investigation of itch. In contrast to pain research, a field with many similarities, rather few scientific attempts have been made to develop and evaluate methods for the quantitative analysis of itch. However, several investigators have recently addressed the challenge of itch measurement in both experimental and clinical situations. This is important, as valid quantitative techniques for the assessment of itch are of considerable value for studying the mechanisms of pruritus, and for the evaluation of antipruritic therapies.